Probing Non-Equilibrium Quantum Many-Body Dynamics with Bright Matter-Wave Solitons

碱金属原子的稀释气体现在通常使用激光冷却到绝对零度的百万分之一，使它们被限制在由于原子与外加磁场或远失谐的非共振激光束相互作用而形成的陷阱中。在这种陷阱中，通过蒸发进一步冷却，在玻色子原子的情况下，会产生一种新的物质状态，称为玻色-爱因斯坦凝聚，其中粒子的量子力学性质主导了它们的经典行为。玻色-爱因斯坦凝聚体在1995年首次被观测到以来，已被成功地用于研究从超流到光学晶格中强关联多体态的基础研究等各种物理现象，为更复杂的凝聚态系统提供了深入的见解。这一成功源于超冷量子气体的两个重要特性。首先，从实验的角度来看，超冷原子气体很容易操纵和控制的外部电磁场（直流，射频，微波和光学），允许在实验配置和高灵敏度的检测非常高的实时灵活性。其次，玻色-爱因斯坦凝聚在理论上已经被证明是容易处理的，这主要是由于它们的稀释、弱相互作用的性质，从而使人们对实验观察有了更深入的理解。这使得超冷量子气体的一个理想的试验场的前沿发展，在我们的理论理解的行为的多体quantum systems.在这里，我们提出了一个计划的基础研究，旨在产生一个更好的一般理解的非平衡相互作用的量子多体系统的动力学，使用原子玻色爱因斯坦凝聚体的85 Rb。具体来说，我们将利用两个85 Rb原子之间的碰撞共振（称为Feshbach共振）来调整凝聚体中的原子相互作用，使其具有吸引力，从而产生明亮的物质波孤子;鲁棒的，非色散的原子波包被限制在一维中传播，其中有吸引力的原子相互作用正好补偿了通常的色散。孤立子是描述各种物理系统的非线性偏微分方程的解。孤子于1834年首次在苏格兰联合运河的浅水中被观察到，此后在许多其他背景下进行了研究，包括非线性光学，生物物理学，天体物理学和粒子物理学。在原子背景下，系统的潜在量子性质引发了复杂的多体量子处理，以准确地捕获基本物理。该提案描述了一个系统的，密切相关的实验理论研究，这种“量子”明亮的物质波孤子，以揭示明亮的孤子的相干性和纠缠特性，同时开发新的先进的理论治疗适用于其他量子多体系统。与该领域的国际领先专家合作，我们的目标是最终评估使用量子亮孤子产生薛定谔猫态用于量子增强干涉测量的可行性。拟议的研究福尔斯属于两个确定的当前物理学重大挑战的范围，即“涌现和远离平衡的物理学”和“新量子技术的量子物理学”，从而在公认的潜在重大社会和经济影响领域为英国科学做出贡献。

Dilute gases of alkali atoms are now routinely cooled to within a millionth of a degree of absolute zero using laser light, permitting them to be confined in traps formed due to the interaction of the atom with either an applied magnetic field or a far-detuned off-resonant laser beam. Further cooling by evaporation in such traps leads, in the case of bosonic atoms, to the creation of a new state of matter, known as a Bose-Einstein condensate, in which the quantum mechanical nature of the particles dominates over their classical behaviour. Such condensates are often viewed as the atomic or matter-wave equivalent of coherent laser light.Since their first observation in 1995, Bose-Einstein condensates have been used with great success to investigate a vast range of physical phenomena from fundamental studies of superfluidity to strongly correlated many-body states in optical lattices, providing insight into more complicated condensed matter systems. This success stems from two important features of ultracold quantum gases. Firstly, from an experimental stand-point, ultracold atomic gases are readily manipulated and controlled with external electromagnetic fields (dc, radio-frequency, microwave and optical) permitting a very high degree of real-time flexibility in the experimental configuration and highly sensitive detection. Secondly, Bose-Einstein condensates have proved theoretically tractable, due largely to their dilute, weakly interacting nature, leading to a deeper understanding of experimental observations. This makes ultracold quantum gases an ideal testing ground for the cutting-edge developments in our theoretical understanding of the behaviour of many-body quantum systems.Here, we propose a program of fundamental research intended to yield a better general understanding of the dynamics of non-equilibrium interacting quantum many-body systems, using atomic Bose-Einstein condensates of 85Rb. Specifically, we will exploit a collision resonance (known as a Feshbach resonance) between two 85Rb atoms to tune the atomic interactions in the condensate to be attractive, thereby generating bright matter-wave solitons; robust, non-dispersive atomic wave-packets confined to propagate in one dimension, in which the attractive atomic interactions exactly compensate the usual dispersion. Solitons arise as solutions to nonlinear partial differential equations describing a diverse range of physical systems. First observed in the shallow water of the Union Canal in Scotland in 1834, solitons have since been studied in many other contexts, including nonlinear optics, biophysics, astrophysics and particle physics. In the atomic context, the underlying quantum nature of the system provokes sophisticated many-body quantum treatments to accurately capture the essential physics. This proposal describes a systematic, closely interlinked experimental-theoretical study of such "quantum" bright matter-wave solitons with a view to exposing the coherence and entanglement properties of bright solitons, whilst developing new advanced theoretical treatments applicable to other quantum many-body systems. Working together with the leading international experts in the field, we aim ultimately to assess the feasibility of using quantum bright solitons to generate Schrödinger cat states for quantum-enhanced interferometry. The proposed research falls within the remit of two of the identified current Grand Challenges in Physics, "Emergence and Physics Far From Equilibrium" and "Quantum Physics for New Quantum Technologies", and thereby contributes to UK science in areas where there is recognised potential for significant societal and economic impact.